Researchers from Emory University have discovered that
norovirus in groundwater can remain infectious for at least 61 days. The
research is published in the October Applied
and Environmental Microbiology.

Human norovirus is the most common cause of acute
gastroenteritis.The disease it causes
tends to be one of the more unpleasant of those that leave healthy people
unscathed in the long run, with diarrhea and vomiting that typically last for
48 hours. Norovirus sickens one in 15 Americans annually, causing 70,000
hospitalizations, and more than 500 deaths annually, according to the Centers
for Disease Control and Prevention.

The results answer a question of great importance to public
health, which had driven researcher Christine Moe and her colleagues Juan Leon and G. Marshall Lyon to conduct
this research: If well water becomes contaminated with noroviruses--perhaps
from leaking sewer lines or a septic tank—how long do these noroviruses survive
in water, and when would it be safe to drink from that well?

To answer that question, they prepared a safety-tested virus
stock solution. They then put a known amount of this solution into a container
of groundwater from an Atlanta well, which had met Environmental Protection Agency
drinking water standards.

The researchers then tested the virus infectivity at days
naught, 4, 14, 21, 27, and 61, by having volunteers drink the water on those
days. The durability of the virus’ infectivity was unexpected, says Moe. Most
of the 13 volunteers became infected at various time points, exhibiting among
them the complete range of norovirus symptoms, which endured for as long as
five days post challenge. “We were surprised to observe that even the
volunteers that drank the water 61 days after we had added the virus still got
infected with the norovirus,” says Moe.

Norovirus may remain infective far longer than 61 days. The
researchers stored the groundwater at room temperature in the dark, using
reverse transcription polymerase chain reaction to determine how much viral RNA
remained after 622 days, and again after 1,266 days. They found no reduction
after the first interval, and very little at the end of the second interval.
Unfortunately, funding was insufficient to test infectivity in human volunteers
beyond day 61.

“This study provides further evidence of the need to treat
groundwater used for drinking water,” says Moe, adding that the Environmental
Protection Agency and other decision-makers who regulate drinking water need to
take these findings into account, particularly since roughly half the US
population relies upon groundwater for drinking.

To ensure that the volunteers’ health would not be
compromised, the investigators conducted the study in a special research unit
of Emory University Hospital, while taking a variety of other precautionary
measures.

Anticipating a question about who would volunteer to
participate in a study with such potentially unpleasant consequences, Moe says
that some volunteers have said that “they want to see how good their immune
system is, and whether they will actually get sick.” Three of the 13 volunteers
did not become sick. One volunteer was the local librarian “who came to the
research unit with a huge bag of books that she wanted to read while she was in
the study,” says Moe.